Diagnose files that aren't in the crate hierarchy

[jonas-schievink]

As of recently, we diagnose mod m; with a #[cfg] that is currently inactive. We do not emit a diagnostic for the contents of m.rs though, which can be pretty confusing, since it just shows up as "IDE is not working" while editing m.rs.

[flodiebold]

It'd also be really great to have a big warning when editing a file that isn't in the module tree at all.

[Kimundi]

According to the Rust discord, warnign about this is also apparently a feature in jetbrains. Would also address issues like this: #7345

[JDuchniewicz]

Can we force rust-analyzer to include the file in the tree?

[jonas-schievink]

I'm planning to add a quickfix that treats files like this as standalone crates instead. Blindly injecting them into the module hierarchy doesn't seem like the best idea.

[JDuchniewicz]

This is probably the best idea, most of the time when you are writing a standalone file, you only need standard completion and features. Unless other people have different experiences.

[jonas-schievink]

I'm planning to add a quickfix that treats files like this as standalone crates instead.

I added a quickfix that adds the appropriate mod name; item instead

[cbrit]

Is this going anywhere? Would be a wonderful feature.